content: /*******************************************************************************
   * Copyright 2011, 2012 Chris Banes.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   * http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   *******************************************************************************/
  package com.handmark.pulltorefresh.library.extras;
  
  import java.util.concurrent.atomic.AtomicBoolean;
  
  import android.content.Context;
  import android.util.AttributeSet;
  import android.webkit.WebView;
  
  import com.handmark.pulltorefresh.library.PullToRefreshWebView;
  
  /**
   * An advanced version of {@link PullToRefreshWebView} which delegates the
   * triggering of the PullToRefresh gesture to the Javascript running within the
   * WebView. This means that you should only use this class if:
   * <p/>
   * <ul>
   * <li>{@link PullToRefreshWebView} doesn't work correctly because you're using
   * <code>overflow:scroll</code> or something else which means
   * {@link WebView#getScrollY()} doesn't return correct values.</li>
   * <li>You control the web content being displayed, as you need to write some
   * Javascript callbacks.</li>
   * </ul>
   * <p/>
   * <p/>
   * The way this call works is that when a PullToRefresh gesture is in action,
   * the following Javascript methods will be called:
   * <code>isReadyForPullDown()</code> and <code>isReadyForPullUp()</code>, it is
   * your job to calculate whether the view is in a state where a PullToRefresh
   * can happen, and return the result via the callback mechanism. An example can
   * be seen below:
   * <p/>
   * 
   * <pre>
   * function isReadyForPullDown() {
   *   var result = ...  // Probably using the .scrollTop DOM attribute
   *   ptr.isReadyForPullDownResponse(result);
   * }
   * 
   * function isReadyForPullUp() {
   *   var result = ...  // Probably using the .scrollBottom DOM attribute
   *   ptr.isReadyForPullUpResponse(result);
   * }
   * </pre>
   * 
   * @author Chris Banes
   */
  public class PullToRefreshWebView2 extends PullToRefreshWebView {
  
  	static final String JS_INTERFACE_PKG = "ptr";
  	static final String DEF_JS_READY_PULL_DOWN_CALL = "javascript:isReadyForPullDown();";
  	static final String DEF_JS_READY_PULL_UP_CALL = "javascript:isReadyForPullUp();";
  
  	public PullToRefreshWebView2(Context context) {
  		super(context);
  	}
  
  	public PullToRefreshWebView2(Context context, AttributeSet attrs) {
  		super(context, attrs);
  	}
  
  	public PullToRefreshWebView2(Context context, Mode mode) {
  		super(context, mode);
  	}
  
  	private JsValueCallback mJsCallback;
  	private final AtomicBoolean mIsReadyForPullDown = new AtomicBoolean(false);
  	private final AtomicBoolean mIsReadyForPullUp = new AtomicBoolean(false);
  
  	@Override
  	protected WebView createRefreshableView(Context context, AttributeSet attrs) {
  		WebView webView = super.createRefreshableView(context, attrs);
  
  		// Need to add JS Interface so we can get the response back
  		mJsCallback = new JsValueCallback();
  		webView.addJavascriptInterface(mJsCallback, JS_INTERFACE_PKG);
  
  		return webView;
  	}
  
  	@Override
  	protected boolean isReadyForPullStart() {
  		// Call Javascript...
  		getRefreshableView().loadUrl(DEF_JS_READY_PULL_DOWN_CALL);
  
  		// Response will be given to JsValueCallback, which will update
  		// mIsReadyForPullDown
  
  		return mIsReadyForPullDown.get();
  	}
  
  	@Override
  	protected boolean isReadyForPullEnd() {
  		// Call Javascript...
  		getRefreshableView().loadUrl(DEF_JS_READY_PULL_UP_CALL);
  
  		// Response will be given to JsValueCallback, which will update
  		// mIsReadyForPullUp
  
  		return mIsReadyForPullUp.get();
  	}
  
  	/**
  	 * Used for response from Javascript
  	 * 
  	 * @author Chris Banes
  	 */
  	final class JsValueCallback {
  
  		public void isReadyForPullUpResponse(boolean response) {
  			mIsReadyForPullUp.set(response);
  		}
  
  		public void isReadyForPullDownResponse(boolean response) {
  			mIsReadyForPullDown.set(response);
  		}
  	}
  }
  